Uplink passive multiple access method and system based on ODMA

Abstract

The invention relates to an uplink passive multiple access method and system based on ODMA, and the method comprises the following steps: S1, at a user side, for each active user, coding data sent by the user according to the characteristics of uplink URA, the transmission characteristics of ODMA and the linear coding characteristics of polarization codes; and S2, decoding the received information at the base station by using a multi-user detection algorithm, an ODMA transmission mode codebook and a polarization code decoding criterion so as to obtain information source information. Simulation results show that compared with other uplink URA schemes based on ODMA, the system has better decoding performance and higher energy efficiency.

Description

Technical Field

[0001] The present invention relates to the technical field of wireless communications, and in particular to an ODMA-based uplink passive multiple access method and system. Background Art

[0002] Massive Machine Type Communications (mMTC) is a key scenario with the greatest potential for achieving large-scale connectivity in the upcoming sixth-generation mobile communication technology (6G). The core mission of mMTC is to provide cellular connectivity for millions of low-speed machine-type devices to support Internet of Things (IoT) applications. This communication mode, primarily based on the uplink, features short data packets, massive device access, low energy consumption, and sporadic communication. Traditional grant-based random access protocols are no longer suitable for mMTC scenarios due to their long scheduling delays and high signaling overhead. In recent years, grant-free random access (GF-RA) and emerging passive random access protocols have garnered widespread attention as promising alternatives. In a GF-RA system, an activated device can send data directly after sending a preamble, without waiting for base station authorization, significantly reducing system access latency and signaling overhead. Traditional GF-RA is often referred to as sourced random access (SRA) because it assigns each user a unique pilot to identify the source of the message.

[0003] In some emerging mMTC applications (such as the Internet of Things), millions of devices intermittently communicate with a common access point. In this scenario, it is impractical to assign a unique pilot to each user due to limited time and frequency resources. To address this problem, Unsourced Random Access (URA) was proposed. URA fundamentally reimagines the large-scale access problem by decoupling user identification from data transmission. Instead of assigning a unique preset or codebook to each potential user, URA uses a common codebook, and the receiver focuses on recovering the transmitted message list. This paradigm shift greatly reduces system complexity and makes it possible to implement a truly large number of devices.

[0004] URA aims to address the data collision problem of large numbers of infrequently active devices in IoT networks by integrating the strengths of information theory, network theory, and coding theory. Leveraging coding theory, the URA protocol cleverly circumvents the complex receiver design and scalability challenges of non-orthogonal multiple access technologies in large-scale access scenarios. Selecting an appropriate codebook significantly improves system capacity, maintaining good performance even with dozens or even hundreds of concurrently active devices. Research has shown that passive random access can significantly reduce the minimum energy per bit required for reliable communication. Therefore, passive random access is expected to become a key technology in future antenna communications. Summary of the Invention

[0005] In view of this, an object of the present invention is to provide an uplink passive multiple access method and system based on ODMA, which is conducive to improving decoding performance and energy efficiency.

[0006] To achieve the above object, the present invention adopts the following technical solution: an uplink passive multiple access method based on ODMA, comprising the following steps:

[0007] Step S1: At the user end, for each active user, encode the user's transmitted data based on the uplink URA characteristics, ODMA transmission characteristics, and the linear coding characteristics of the polar code;

[0008] Step S2: At the base station, the received information is decoded using a multi-user detection algorithm, an ODMA transmission mode codebook, and a polar code decoding criterion, thereby obtaining information source information.

[0009] In a preferred embodiment, step S1 includes the following steps:

[0010] Step S11: In the uplink URA system, a central base station with M receiving antennas supports K base stations equipped with a single transmitting antenna. tot User; During any transmission period, there are K a K users are active tot >>K a ; Each active user sends a B-bit message to the base station through n channels; for the k-th active user, the message u k =(u ks ,u kc ) is divided into u ks and u kc , the lengths are B s and B c =BB s ;

[0011] Step S12: Define mapping: where [J] = {1,...,J}, and Length B s The binary message u ks Convert to decimal index D by mapping k =Ω(u ks ); according to u ks The decimal index D k Selecting a common pilot codebook D k column vector As the pilot symbol of the k-th active user, the column vector of the common pilot codebook P is normalized to ||p i || 2 =n p P p , n p is the length of the pilot symbol, P p is the average symbol power of the pilot symbol, ||·|| is the Euclidean norm;

[0012] Step S13: According to u ks The decimal index D k Select a common switch-mode codebook A∈{0,1} n×J D k column vector As the switching pattern vector transmitted by the k-th active user, the public switching pattern codebook A is a randomly generated binary regular sparse matrix with a Hamming weight of n for each column. d , the Hamming weight of each row is n d J / n,n d The length of all symbols sent by the user, including pilot symbols and data symbols;

[0013] Step S14, length is B c The binary message u kc First use the B crc The cyclic redundancy check code CRC of the bit is encoded to generate a length of B c +B crc The CRC code word is the CRC code word of the message u kc The CRC codeword is obtained by using (n c ,B c +B crc ) Polar code encoder generates codeword information The polar code is generated according to the Bhattacharyya parameter construction method, and the frozen bits use an all-zero bit sequence;

[0014] Step S15, v k Generated by Quadrature Phase Shift Keying (QPSK) in T represents the transpose operation, P d represents the average symbol power of data symbols;

[0015] Step S16: and w k Cascade

[0016] Step S17: Pass Mode After processing, a switch symbol sequence is generated where n d =n c / 2+n p Specifically, n of the n channels d channels are used to transmit symbol sequences s k , other d channels are idle; this operation is performed by Indicates that the i-th channel is used for message transmission, Indicates that the i-th channel is an idle channel.

[0017] In a preferred embodiment, step S2 includes the following steps:

[0018] Step S21: In the uplink URA system, it is assumed that the n-dimensional quasi-static Rayleigh fading channel coefficient remains constant during each transmission frame; the signal received by the base station Expressed as:

[0019]

[0020] in, is the transmission signal matrix, is the equivalent channel matrix, represents the channel coefficient vector between user k and the M receiving antennas of the base station, is the large-scale fading coefficient, represents the small-scale fading of independent and identically distributed elements, that is It is a cyclically symmetric complex additive Gaussian white noise consisting of independent and identically distributed elements with zero mean and variance N0, that is,

[0021] Step S22: Estimate the total number of active users using formula (2)

[0022]

[0023] in, represents the signal received by the i-th antenna;

[0024] Step S23, active pilot and mode detection: first, active pilot detection is performed; for the k-th active user, the switch symbol sequence sent by the user is the concatenation of the pilot symbol and the data symbol, and then the corresponding switch mode is used. After processing, the pilot signal is generated in the switching mode The first n p The public pilot codebook P is transmitted in the channel corresponding to the active index, which only accounts for a small part of the switch symbol sequence; therefore, the public pilot codebook P cannot be directly used for active pilot detection;

[0025] From the transmitter, the pilot symbol and switch mode It is a one-to-one correspondence relationship, and this feature is used to expand the common pilot codebook P; specifically, the pilot transmission mode index is used to construct an extended common pilot matrix based on the switching mode The elements of the i-th column of the public pilot codebook P are converted into the first n elements of the i-th column of the public switching mode codebook A. p The active index is placed in the i-th column of P′, and the elements in the other columns are all zero;

[0026] The extended common pilot matrix P′ also contains pilot information, and P′ is used for active pilot and pattern detection; since K a The problem of identifying the columns of P′ is transformed into a compressed sensing problem with P′ as the measurement matrix. The generalized orthogonal matching pursuit algorithm gOMP is used to detect active pilots. In each iteration of gOMP, the correlation between the current residual of the received signal and the columns of P′ is first calculated using antenna diversity technology:

[0027]

[0028] in, H represents the complex conjugate transpose, Y (t) [:,i] represents the residual of the received signal on the i-th antenna at the t-th iteration of gOMP. Here, the programming notation is used. Y[:,i] and Y[j,:] represent the i-th column and j-th row of the matrix Y respectively. Define Y (0) =Y, each round of iteration takes C (t) The largest elements and add the index corresponding to the selected element to the gOMP output list In, n gOMP represents the number of iterations of gOMP, Indicates rounding up, Δ is a decimal between 0 and 1;

[0029] The residual of the received signal is updated using formula (4) and used for the next gOMP iteration:

[0030]

[0031] in, represents the set of all pilot indices detected by gOMPt iterations, is Determine the column set of P′, I b is the b×b identity matrix; when the number of iterations reaches n gOMP At this point, the iteration ends and gOMP outputs the detected active user mode index and the corresponding extended pilot Since the pilot and pattern index are sent by the user, s bits are determined, so the user's first B s Bit Information It is also decoded at this step;

[0032] Step S24: Channel estimation: Obtain active user pattern index and the corresponding extended pilot Then, the linear minimum mean square error estimation LMMSE is used to estimate the channel information of active users:

[0033]

[0034] Among them, Y (j) represents the residual of the received signal in the jth decoding iteration;

[0035] Step S25: Eliminate pilot pollution; use active users to expand the pilot matrix Eliminate the received signal residual Y of this round of decoding iteration (j) Pilot information interference:

[0036]

[0037] in, represents the received signal residual Y in the jth decoding iteration (j) An estimate of the received data signal after pilot contamination removal;

[0038] Step S26, symbol estimation: using LMMSE to separate users:

[0039]

[0040] in, Represents a set of estimated active user switch pattern sequence symbols; given an active user pattern index and estimation of active user switching pattern sequence symbols We can obtain the data symbol estimation vector for each user in Indicated by Determine the active data index specified After passing through the QPSK demodulator, the input symbol of the channel decoder is obtained

[0041] Step S27, channel decoding: For the k-th active user, the input symbol is estimated by treating the interference as noise TIN. As the output of a single-user channel, we can use formula (8) to get Extract the log-likelihood ratio LLR bit by bit,

[0042]

[0043] Then β k Send it to the single user continuous cancellation list SCL decoder, the decoder will output n L A list of the most likely messages, and then use the CRC decoder to select the message that meets the constraints, and the most reliable decoding sequence that satisfies the CRC check is considered valid; the and The decoded message after merging Add to message list and index it Add to the index set successfully decoded in this iteration middle;

[0044] Step S28: After re-encoding, modulating and switching mode processing all successfully decoded messages, regenerate the switching symbol sequence matrix for actual transmission.

[0045] Step S29: Ignore the interference of undecoded users and use the reconstructed transmit signal matrix To re-estimate the channel vector:

[0046]

[0047] Step S210: Using the reconstructed transmit signal matrix and re-estimate the channel vector Perform successive interference cancellation (SIC) and obtain the received signal residual Y for the next decoding iteration. (j+1) :

[0048]

[0049] After SIC, the user mode index of the successfully decoded message from Remove

[0050] Step S211: When all active users' messages are successfully decoded or the latest decoding iteration fails to decode any new messages, the decoding iteration is stopped and the message list is output. This is the source information that has been successfully decoded; otherwise, S24-S210 will be repeated.

[0051] The present invention provides an uplink passive multiple access system based on ODMA, comprising a memory, a processor, and computer program instructions stored in the memory and capable of being executed by the processor. When the processor executes the computer program instructions, an uplink passive multiple access method based on ODMA can be implemented.

[0052] Compared with the existing technology, the present invention has the following advantages: the present invention proposes a transmission scheme, in which the transmitting user uses switch division multiple access technology to extend its pilot sequence and polarization codeword into the transmission frame based on the ODMA transmission mode. This transmission scheme greatly reduces the data interference between users; at the receiving end, the present invention designs a pilot interference elimination module that matches the transmission scheme. This module improves the symbol estimation performance by removing the interference of pilot symbols before the symbol estimation stage. The present invention has a lower minimum energy ratio than other URA schemes under the same environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] Figure 1 A diagram illustrating a method implementation model of an embodiment of the present invention;

[0054] Figure 2 This is a data encoding flow chart of the transmitting end of the solution proposed in an embodiment of the present invention;

[0055] Figure 3 This is a message recovery flow chart of the receiving end of the solution proposed in an embodiment of the present invention;

[0056] Figure 4 Comparison of per-user error probability simulation curves of the proposed scheme and other ODMA schemes under 100 users. DETAILED DESCRIPTION

[0057] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0058] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the present application belongs.

[0059] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application; as used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form, and it should be understood that when the terms "comprise" and / or "include" are used in this specification, they indicate the presence of features, steps, operations, devices, components and / or their combinations.

[0060] like Figure 1 As shown, this embodiment provides an uplink passive multiple access system design based on ODMA, including the following steps:

[0061] Step S1: At the user end, for each active user, encode the user's transmitted data based on the uplink URA characteristics, ODMA transmission characteristics, and the linear coding characteristics of the polar code;

[0062] Step S2: At the base station, the received information is decoded using a multi-user detection algorithm, an ODMA transmission mode codebook, and a polar code decoding criterion, thereby obtaining information source information.

[0063] Furthermore, step S1 includes the following steps:

[0064] Step S11: In the uplink URA system, a central base station with M receiving antennas supports K base stations equipped with a single transmitting antenna. tot During any transmission, there are K a users are active (K tot >>K a ). Each active user sends a B-bit message to the base station through n channels. For the k-th active user, the message u k =(u ks ,u kc ) is divided into u ks and u kc , the lengths are B s and B c =BB s .

[0065] Step S12: Define mapping: where [J] = {1,...,J}, and Length B s The binary message u ks Convert to decimal index D by mapping k =Ω(u ks ). According to u ks The decimal index D k Selecting a common pilot codebook D k column vector As the pilot symbol of the k-th active user, the column vector of the common pilot codebook P is normalized to ||p i || 2 =n p P p , n p is the length of the pilot symbol, P p is the average symbol power of the pilot symbols, and ||·|| is the Euclidean norm.

[0066] Step S13: According to u ks The decimal index D k Select a common switch-mode codebook A∈{0,1} n×J D k column vector As the switching pattern vector transmitted by the k-th active user, the public switching pattern codebook A is a randomly generated binary regular sparse matrix with a Hamming weight of n for each column. d , the Hamming weight of each row is n d J / n,n d The length of all symbols sent by the user, including pilot symbols and data symbols.

[0067] Step S14, length is B c The binary message u kc First use the B crc The cyclic redundancy check code (CRC) of the bit is encoded to generate a length of B c +B crc The CRC code word is the CRC code word of the message u kc The CRC codeword is generated by concatenating the CRC bits output by the CRC encoder. c ,B c +B crc ) Polar code encoder generates codeword information The polar code is generated according to the Bhattacharyya parameter construction method, and the frozen bits use an all-zero bit sequence.

[0068] Step S15, v k Generated by Quadrature Phase Shift Keying (QPSK) in T represents the transpose operation, P d Represents the average symbol power of data symbols.

[0069] Step S16: and w k Cascade

[0070] Step S17: Pass Mode After processing, a switch symbol sequence is generated where n d =n c / 2+n p Specifically, n of the n channels d channels are used to transmit symbol sequences s k , other d The channel is in idle state. Indicates that the i-th channel is used for message transmission, Indicates that the i-th channel is an idle channel.

[0071] Furthermore, step S2 includes the following steps:

[0072] Step S21: In the uplink URA system, it is assumed that the n-dimensional quasi-static Rayleigh fading channel coefficient remains constant during each transmission frame. It can be expressed as:

[0073]

[0074] in, is the transmission signal matrix, is the equivalent channel matrix, represents the channel coefficient vector between user k and the M receiving antennas of the base station, is the large-scale fading coefficient, represents the small-scale fading of independent and identically distributed elements, that is It is a cyclically symmetric complex additive Gaussian white noise consisting of independent and identically distributed elements with zero mean and variance N0, that is,

[0075] Step S22: Estimate the total number of active users using formula (2)

[0076]

[0077] in, represents the signal received by the i-th antenna.

[0078] Step S23, active pilot and pattern detection: In order to decode the sent message sequence, we must first perform active pilot detection. For the k-th active user, the switch symbol sequence sent by the user is the concatenation of the pilot symbol and the data symbol, and then the corresponding switch pattern. After processing, the pilot signal is generated in the switching mode The first n pThe public pilot codebook P is transmitted in the channel corresponding to the active index, which only accounts for a small part of the switch symbol sequence. Therefore, the public pilot codebook P cannot be directly used for active pilot detection.

[0079] It can be seen from the transmitting end that the pilot symbol and switch mode There is a one-to-one correspondence between them. We use this property to expand the common pilot codebook P. Specifically, we construct an extended common pilot matrix based on the switching mode using the pilot transmission mode index. The elements of the i-th column of the public pilot codebook P are converted into the first n elements of the i-th column of the public switching mode codebook A. p The activity index is placed in the i-th column of P′, and the elements in the remaining columns are all zero.

[0080] The extended common pilot matrix P′ also contains pilot information, and we use P′ for active pilot and pattern detection. a The problem of identifying the columns of P′ can be transformed into a compressed sensing problem with P′ as the measurement matrix. We use the generalized orthogonal matching pursuit (gOMP) algorithm to detect active pilots. In each iteration of gOMP, we first use antenna diversity technology to calculate the correlation between the current residual of the received signal and the columns of P′:

[0081]

[0082] in, H represents the complex conjugate transpose, Y (t) [:,i] represents the residual of the received signal on the i-th antenna at the t-th iteration of gOMP. Here, we use the programming notation, and Y[:,i] and Y[j,:] represent the i-th column and j-th row of the matrix Y, respectively. We define Y (0) =Y, in each iteration we take C (t) The largest elements and add the index corresponding to the selected element to the gOMP output list In, n gOMP represents the number of iterations of gOMP, Indicates rounding up, where Δ is a decimal between 0 and 1.

[0083] We use formula (4) to update the residual of the received signal and use it for the next gOMP iteration:

[0084]

[0085] in, gOMP tThe set of all pilot indices detected in the iteration, is Determine the column set of P′, I b is a b×b identity matrix. When the number of iterations reaches n gOMP At this point, the iteration ends and gOMP outputs the detected active user mode index and the corresponding extended pilot Since the pilot and pattern index are sent by the user, s bits are determined, so the user's first B s Bit Information It is also decoded at this step.

[0086] Step S24: Channel estimation: Obtain active user pattern index and the corresponding extended pilot Finally, we use Linear Minimum Mean Square Error (LMMSE) to estimate the channel information of active users:

[0087]

[0088] Among them, Y (j) represents the residual of the received signal in the jth decoding iteration.

[0089] Step S25, pilot contamination elimination: After the data symbols are processed by the switching mode, the number of users transmitting on the same channel is reduced, but the problem of data interference between users still exists. For example, for the k-th active user, the channel where its data symbols are transmitted may also contain pilot symbols and data symbols of other users, which will affect the accuracy of symbol estimation in the next stage. Therefore, we use the active user to expand the pilot matrix Eliminate the received signal residual Y of this round of decoding iteration (j) Pilot information interference:

[0090]

[0091] in, represents the received signal residual Y in the jth decoding iteration (j) An estimate of the received data signal after pilot contamination removal.

[0092] Step S26, symbol estimation: To obtain the estimated transmitted signal matrix, we use LMMSE to separate the users:

[0093]

[0094] in, Represents the set of estimated active user switch pattern sequence symbols. Given an active user pattern index and estimation of active user switching pattern sequence symbols We can obtain the data symbol estimation vector for each user in Indicated by Determine the active data index specified After passing through the QPSK demodulator, the input symbol of the channel decoder is obtained.

[0095] Step S27, channel decoding: For the k-th active user, we use the method of treating interference as noise (TIN) to estimate the input symbol As the output of a single-user channel, we can use formula (8) to get Extract the log-likelihood ratio (LLR) bit by bit

[0096]

[0097] Then β k Send it to the single user continuous cancellation list SCL decoder, the decoder will output n L A list of the most likely messages, and then use the CRC decoder to select the message that meets the constraints, and the most reliable decoding sequence that satisfies the CRC check is considered valid. We take the and The decoded message after merging Add to message list and index it Add to the index set successfully decoded in this iteration middle.

[0098] Step S28: We re-encode, modulate and perform switch mode processing on all successfully decoded messages and regenerate the switch symbol sequence matrix for actual transmission.

[0099] Step S29: Ignoring the interference of undecoded users, we use the reconstructed transmit signal matrix To re-estimate the channel vector:

[0100]

[0101] Step S210: Using the reconstructed transmit signal matrix and re-estimate the channel vector Successive Interference Cancellation (SIC) is performed to subtract the interference caused by the decoded user and obtain the received signal residual Y for the next decoding iteration. (j+1) :

[0102]

[0103] After SIC, the user mode index of the successfully decoded message from Remove from .

[0104] Step S211: When all active users' messages are successfully decoded or the latest decoding iteration fails to decode any new messages, the decoding iteration is stopped and the message list is output. Otherwise, steps S24 to S210 are repeated.

[0105] This embodiment also provides an ODMA-based uplink passive multiple access system design, including a memory, a processor, and computer program instructions stored in the memory and capable of being executed by the processor. When the processor executes the computer program instructions, the above method steps can be implemented.

[0106] Experimental simulation

[0107] This section simulates the user performance of the proposed system under 100 active users, where n = 3200, B = 100, M = 50, and n c =1024, B s =15, B crc =16,n L =128. The pilot length n of the proposed system p The pilot length of the first two systems is 400, while the pilot length of the other two systems is 600. To ensure fairness, the transmit power of all systems is kept consistent. As can be seen from the figure, our solution can achieve a performance gain of approximately 0.4dB compared to the other two solutions. This means that our solution can achieve the same per-user error probability with a lower energy ratio, which is more energy-efficient.

[0108] In summary, the present invention proposes an uplink passive multiple access transmission scheme based on ODMA. Transmitting users utilize switch-division multiple access (SDMA) technology to extend their pilot sequences and polarization codewords into the transmission frame based on the ODMA transmission mode. This transmission scheme significantly reduces inter-user data interference. At the receiving end, the present invention designs a pilot interference cancellation module that matches the transmission scheme. This module improves symbol estimation performance by removing interference from pilot symbols before the symbol estimation stage. Under the same conditions, the present invention achieves a lower minimum energy ratio than other URA schemes.

[0109] Those skilled in the art will appreciate that the embodiments of the present application can be provided as methods, systems, or computer program products. Therefore, the present application can adopt the form of a complete hardware embodiment, a complete software embodiment, or an embodiment in combination with software and hardware. Moreover, the present application can adopt the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to magnetic disk storage, CD-ROM, optical storage, etc.) that contain computer-usable program code.

[0110] The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of the processes and / or boxes in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the steps in the process. Figure 1 a process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0111] These computer program instructions may also be stored in a computer readable memory that can direct a computer or other programmable data processing device to work in a specific manner, so that the instructions stored in the computer readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 a process or multiple processes and / or boxes Figure 1 The function specified in one or more boxes.

[0112] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing the instructions executed on the computer or other programmable device for implementing the process. Figure 1 a process or multiple processes and / or boxes Figure 1 A step that specifies a function in one or more boxes.

[0113] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any other manner. Any person skilled in the art may utilize the above-disclosed technical content to modify or modify the present invention into equivalent embodiments. However, any simple modifications, equivalent variations, and modifications to the above embodiments that do not depart from the technical content of the present invention and are based on the technical essence of the present invention remain within the scope of protection of the present invention.

Claims

1. An uplink passive multiple access method based on ODMA, characterized in that: The following steps are involved: Step S1: At the user end, for each active user, encode the user's transmitted data based on the uplink URA characteristics, ODMA transmission characteristics, and the linear coding characteristics of the polar code; Step S2: At the base station, the received information is decoded using a multi-user detection algorithm, an ODMA transmission mode codebook, and a polar code decoding criterion, thereby obtaining information source information.

2. The uplink passive multiple access method based on ODMA according to claim 1, characterized in that: Step S1 includes the following steps: Step S11: In the uplink URA system, a central base station with M receiving antennas supports K base stations equipped with a single transmitting antenna. tot User; During any transmission period, there are K a K users are active tot >>K a ; Each active user sends a B-bit message to the base station through n channels; for the k-th active user, the message u k =(u ks ,u kc ) is divided into u ks and u kc , the lengths are B s and B c =BB s ; Step S12: Define mapping: where [J] = {1,...,J}, and Length B s The binary message u ks Convert to decimal index D by mapping k =Ω(u ks ); according to u ks The decimal index D k Selecting a common pilot codebook D k column vector As the pilot symbol of the k-th active user, the column vector of the common pilot codebook P is normalized to ||p i || 2 =n p P p , n p is the length of the pilot symbol, P p is the average symbol power of the pilot symbol, ||·|| is the Euclidean norm; Step S13: According to u ks The decimal index D k Select a common switch-mode codebook A∈{0,1} n×J D k column vector As the switching pattern vector transmitted by the k-th active user, the public switching pattern codebook A is a randomly generated binary regular sparse matrix with a Hamming weight of n for each column. d , the Hamming weight of each row is n d J / n,n d The length of all symbols sent by the user, including pilot symbols and data symbols; Step S14, length is B c The binary message u kc First use the B crc The cyclic redundancy check code CRC of the bit is encoded to generate a length of B c +B crc The CRC code word is the CRC code word of the message u kc The CRC codeword is obtained by using (n c ,B c +B crc ) Polar code encoder generates codeword information The polar code is generated according to the Bhattacharyya parameter construction method, and the frozen bits use an all-zero bit sequence; Step S15, v k Generated by Quadrature Phase Shift Keying (QPSK) in T represents the transpose operation, P d represents the average symbol power of data symbols; Step S16: and w k Cascade Step S17: Pass Mode After processing, a switch symbol sequence is generated where n d =n c / 2+n p Specifically, n of the n channels d channels are used to transmit symbol sequences s k , other d channels are idle; this operation is performed by Indicates that the i-th channel is used for message transmission, Indicates that the i-th channel is an idle channel.

3. The uplink passive multiple access method based on ODMA according to claim 1, characterized in that: Step S2 includes the following steps: Step S21: In the uplink URA system, it is assumed that the n-dimensional quasi-static Rayleigh fading channel coefficient remains constant during each transmission frame; the signal received by the base station Expressed as: in, is the transmission signal matrix, is the equivalent channel matrix, represents the channel coefficient vector between user k and the M receiving antennas of the base station, is the large-scale fading coefficient, represents the small-scale fading of independent and identically distributed elements, that is It is a cyclically symmetric complex additive Gaussian white noise consisting of independent and identically distributed elements with zero mean and variance N0, that is, Step S22: Estimate the total number of active users using formula (2) in, represents the signal received by the i-th antenna; Step S23, active pilot and mode detection: first, active pilot detection is performed; for the k-th active user, the switch symbol sequence sent by the user is the concatenation of the pilot symbol and the data symbol, and then the corresponding switch mode is used. After processing, the pilot signal is generated in the switching mode The first n p The public pilot codebook P is transmitted in the channel corresponding to the active index, which only accounts for a small part of the switch symbol sequence; therefore, the public pilot codebook P cannot be directly used for active pilot detection; From the transmitter, the pilot symbol and switch mode It is a one-to-one correspondence relationship, and this feature is used to expand the common pilot codebook P; specifically, the pilot transmission mode index is used to construct an extended common pilot matrix based on the switching mode The elements of the i-th column of the public pilot codebook P are converted into the first n elements of the i-th column of the public switching mode codebook A. p The active index is placed in the i-th column of P′, and the elements in the other columns are all zero; The extended common pilot matrix P′ also contains pilot information and is used as the active pilot and mode detection; since K a <<J, the problem of identifying the selected columns of P′ is transformed into a compressive sensing problem with P′ as the measurement matrix, and the generalized orthogonal matching pursuit algorithm gOMP is used to detect the active pilot; in each iteration of gOMP, first, the antenna diversity technology is used to calculate the correlation between the current residual of the received signal and the columns of P′: in, H represents the complex conjugate transpose, Y (t) [:,i] represents the residual of the received signal on the i-th antenna at the t-th iteration of gOMP. Here, the programming notation is used. Y[:,i] and Y[j,:] represent the i-th column and j-th row of the matrix Y respectively. Define Y (0) =Y, each round of iteration takes C (t) The largest elements and add the index corresponding to the selected element to the gOMP output list In, n gOMP represents the number of iterations of gOMP, Indicates rounding up, Δ is a decimal between 0 and 1; The residual of the received signal is updated using formula (4) and used for the next gOMP iteration: in, gOMP t The set of all pilot indices detected in the iteration, is Determine the column set of P′, I b is the b×b identity matrix; when the number of iterations reaches n gOMP At this point, the iteration ends and gOMP outputs the detected active user mode index and the corresponding extended pilot Since the pilot and pattern index are sent by the user, s bits are determined, so the user's first B s Bit Information It is also decoded at this step; Step S24: Channel estimation: Obtain active user pattern index and the corresponding extended pilot Then, the linear minimum mean square error estimation LMMSE is used to estimate the channel information of active users: Among them, Y (j) represents the residual of the received signal in the jth decoding iteration; Step S25: Eliminate pilot pollution; use active users to expand the pilot matrix Eliminate the received signal residual Y of this round of decoding iteration (j) Pilot information interference: in, represents the received signal residual Y in the jth decoding iteration (j) An estimate of the received data signal after pilot contamination removal; Step S26, symbol estimation: using LMMSE to separate users: in, Represents a set of estimated active user switch pattern sequence symbols; given an active user pattern index and estimation of active user switching pattern sequence symbols We can obtain the data symbol estimation vector for each user in Indicated by Determine the active data index specified After passing through the QPSK demodulator, the input symbol of the channel decoder is obtained Step S27, channel decoding: For the k-th active user, the input symbol is estimated by treating the interference as noise TIN. As the output of a single-user channel, we can use formula (8) to get Extract the log-likelihood ratio LLR bit by bit, Then β k Send it to the single user continuous cancellation list SCL decoder, the decoder will output n L A list of the most likely messages, and then use the CRC decoder to select the message that meets the constraints, and the most reliable decoding sequence that satisfies the CRC check is considered valid; the and The decoded message after merging Add to message list and index it Add to the index set successfully decoded in this iteration middle; Step S28: After re-encoding, modulating and switching mode processing all successfully decoded messages, regenerate the switching symbol sequence matrix for actual transmission. Step S29: Ignore the interference of undecoded users and use the reconstructed transmit signal matrix To re-estimate the channel vector: Step S210: Using the reconstructed transmit signal matrix and re-estimate the channel vector Perform successive interference cancellation (SIC) and obtain the received signal residual Y for the next decoding iteration. (j+1) : After SIC, the user mode index of the successfully decoded message from Remove Step S211: When all active users' messages are successfully decoded or the latest decoding iteration fails to decode any new messages, the decoding iteration is stopped and the message list is output. This is the source information that has been successfully decoded; otherwise, S24-S210 will be repeated.

4. An uplink passive multiple access system based on ODMA, characterized in that: The invention comprises a memory, a processor and computer program instructions stored in the memory and capable of being executed by the processor. When the processor executes the computer program instructions, an ODMA-based uplink passive multiple access method as described in any one of claims 1 to 4 can be implemented.

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